U.S. patent number 7,190,389 [Application Number 09/611,364] was granted by the patent office on 2007-03-13 for stereo camera.
This patent grant is currently assigned to Pentax Corporation. Invention is credited to Tetsuya Abe, Takayuki Sensui.
United States Patent |
7,190,389 |
Abe , et al. |
March 13, 2007 |
Stereo camera
Abstract
A stereo camera includes a pair of photographing optical systems
arranged in a common plane so that a common photographing coverage
occurs between a pair of photographing areas taken by the pair of
photographing optical systems, an object distance measuring device,
a convergence angle adjustment mechanism adapted to vary an angle
of convergence defined by, and between, the optical axes of the
pair of photographing optical systems, so as to adjust an amount of
common photographic coverage of the pair of photographing optical
systems, and a controller adapted to control the convergence angle
adjustment mechanism in accordance with object distance data
obtained by the object distance measuring device.
Inventors: |
Abe; Tetsuya (Tokyo,
JP), Sensui; Takayuki (Tokyo, JP) |
Assignee: |
Pentax Corporation (Tokyo,
JP)
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Family
ID: |
16302372 |
Appl.
No.: |
09/611,364 |
Filed: |
July 6, 2000 |
Foreign Application Priority Data
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Jul 7, 1999 [JP] |
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11-193107 |
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Current U.S.
Class: |
348/42; 382/154;
348/E13.016; 348/E13.014 |
Current CPC
Class: |
G03B
35/08 (20130101); H04N 13/239 (20180501); H04N
13/246 (20180501) |
Current International
Class: |
H04N
13/00 (20060101) |
Field of
Search: |
;348/42,47,49,218,139,51,44,36,48,261,208,262 ;382/103,106,154 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0830034 |
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Mar 1998 |
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EP |
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10155104 |
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Jun 1998 |
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JP |
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Primary Examiner: Dastouri; Mehrdad
Assistant Examiner: Senfi; Behrooz
Attorney, Agent or Firm: Greenblum & Bernstein,
P.L.C.
Claims
What is claimed is:
1. A stereo camera comprising: a pair of photographing optical
systems that produce a corresponding pair of photographing areas,
said pair of photographing optical systems being located in a
common plane to produce a common photographing coverage between
each of the pair of photographing areas, each photographing optical
system including an image pickup device that performs a passive
distance measurement of an object distance; an object distance
measuring device that performs an active distance measurement to
measure a distance to an object; a convergence angle adjustment
mechanism that varies an angle of convergence, defined by optical
axes of said pair of photographing optical systems, to adjust an
amount of the common photographic coverage of said pair of
photographing optical systems; and a controller that controls each
of the pair of photographing optical systems to perform the passive
distance measurement of an object distance until such time as a
release button is depressed at least by a half step, controls the
object distance measuring device to perform the active distance
measurement after the release button is depressed at least by a
half step, and controls the convergence angle adjustment mechanism
in accordance with object distance data corresponding to the
measured distance to the object obtained by the active distance
measurement.
2. The stereo camera according to claim 1, wherein said pair of
photographing optical systems each comprise a photographing lens
and an image pickup device, and said convergence angle adjustment
mechanism comprises a drive mechanism which rotates each
photographing optical system to vary the angle of convergence in a
direction to make median lines of field angles of said pair of
photographic optical systems intersect each other.
3. The stereo camera according to claim 2, wherein said drive
mechanism comprises: a pair of rotary plates having respective
center axes of rotation in parallel with each other, said pair of
rotary plates supporting said pair of photographing optical systems
and having inter-meshing sector gears; a sector worm wheel provided
on one of said rotary plates; and a worm which is in mesh with said
sector worm wheel, said worm being secured to a drive shaft of a
motor.
4. The stereo camera according to claim 1, wherein said convergence
angle adjustment mechanism comprises a variable angle prism
provided in a light path of each said pair of photographing optical
systems.
5. The stereo camera according to claim 1, wherein said convergence
angle adjustment mechanism comprises a drive mechanism that moves
at least a part of each of said pair of photographing optical
systems in a direction of a base length of said pair of
photographing optical systems.
6. The stereo camera according to claim 1, said controller further
controlling each of the pair of photographing optical systems to
perform photometering operations until said release button is
depressed at least by a half step.
7. The stereo camera according to claim 1, said controller further
controlling each of the pair of photographing optical systems to
perform autoexposure and/or autofocus operations until said release
button is depressed at least by a half step.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a stereo camera which takes a
three-dimensional picture (stereoscopic photograph) for use in an
optical system which gives a sensation of image depth to a viewer,
due to a parallax produced between the viewer's eyes and
convergence of the viewer's eyes.
2. Description of the Related Art
Upon taking a picture using a stereo camera (stereoscopic camera)
in which images of an object are recorded by at least a pair of
photographing optical systems in a symmetrical arrangement in the
lateral direction, if the object distance is relatively small or
the photographing optical systems are made of telephotographic
optical systems, the photographic coverage (overlap) of right and
left field angles is made small, and hence it is difficult to
obtain a three-dimensional photograph.
A known solution thereto is to give an angle of convergence to the
right and left photographing optical axes to thereby reduce the
parallax between the eyes. However, in most conventional cameras,
the provision of the angle of convergence is troublesomely carried
out by a manual operation.
SUMMARY OF THE INVENTION
It is an object of the present invention to eliminate the drawbacks
of the prior art mentioned above by providing a stereo camera which
can take high-quality three-dimensional photographs by providing an
appropriate angle of convergence between the right and left
photographing optical axes without a complex operation, even if the
object distance is relatively small or telephotographic
photographing systems are used.
To achieve the object mentioned above, according to the present
invention, a stereo camera is provided, including a pair of
photographing optical systems arranged in a common plane so that a
common photographing coverage occurs between a pair of
photographing areas taken by the pair of photographing optical
systems, an object distance measuring device, a convergence angle
adjustment mechanism adapted to vary an angle of convergence
defined by, and between, the optical axes of the pair of
photographing optical systems, so as to adjust the amount of common
photographic coverage of the pair of photographing optical systems,
and a controller adapted to control the convergence angle
adjustment mechanism in accordance with object distance data
obtained by the object distance measuring device.
With this arrangement, no manual adjustment of the angle of
convergence every time the object distance changes is necessary,
and hence the operation efficiency can be enhanced.
In an embodiment, the pair of photographing optical systems are
each included of a photographing lens and an image pickup device.
The convergence angle adjustment mechanism includes a drive
mechanism which rotates each photographing optical system to vary
the angle of convergence in a direction to make median lines of
field angles of the pair of photographing optical systems intersect
each other.
For example, the drive mechanism can include a pair of rotary
plates whose center axes of rotation are parallel with each other,
each of the rotary plates supporting each respective pair of
photographing optical systems; sector gears provided on each of the
pair of rotary plates, the sector gears of one of the pair of
rotary plates being in mesh with the sector gear the other of the
pair of rotary plates; a sector worm wheel provided on one of the
rotary plates; and a worm which is in mesh with the sector worm,
the worm being secured to a drive shaft of a motor.
In another embodiment, the convergence angle adjustment mechanism
includes a variable angle prism provided in a light path of each
the pair of photographing optical systems.
In another embodiment, the convergence angle adjustment mechanism
includes a drive mechanism which moves at least a part of each the
pair of photographing optical system in a direction of the base
length of the pair of photographing optical systems.
In an embodiment, each of the pair of photographing optical systems
is provided with a respective first and second image pickup device,
wherein when passive measurements of the object distance are
carried out by the first and second image pickup devices,
measurement points for each of the first and second image pickup
devices are located on a side of the field angle thereof, with
respect to the median line thereof, closest to a corresponding
respective one of the second and first image pickup devices.
The stereo camera can be applied to an electronic still camera.
According to another aspect of the present invention, a stereo
camera is provided, including at least a pair of photographing
optical systems arranged in a common plane, and a convergence angle
control device which varies an angle of convergence defined by and
between the optical axes of the pair of photographing optical
systems in accordance with object distance data.
According to another aspect of the present invention, a stereo
camera is provided, including a pair of photographing optical
systems arranged in a common plane so that a common photographing
coverage occurs between a pair of photographing areas taken by the
pair of photographing optical systems, an object distance measuring
device, a photographic coverage adjustment device adapted to adjust
an amount of the photographic coverage of the pair of photographing
optical systems, and a controller adapted to control the
photographic coverage adjustment device in accordance with object
distance data obtained by the object distance measuring device.
The present disclosure relates to subject matter contained in
Japanese Patent Application No. 11-193107 (filed on Jul. 7, 1999)
which is expressly incorporated herein by reference in its
entirety.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be discussed below in detail with reference to
the accompanying drawings, in which:
FIG. 1 is a perspective view of a first embodiment of a stereo
camera according to the present invention;
FIG. 2 is a schematic view of right and left photographing optical
systems having substantially parallel photographing optical axes,
in a stereo camera according to a first embodiment of the present
invention;
FIG. 3 is a schematic view of right and left photographing optical
systems whose optical axes define therebetween an angle of
convergence, in a stereo camera according to a first embodiment of
the present invention;
FIG. 4 is a perspective view of right and left photographing units
and a drive mechanism thereof, in a stereo camera according to a
first embodiment of the present invention;
FIGS. 5A and 5B schematically show a plan view and a front
elevational view, of right and left photographing units and a drive
mechanism thereof, shown in FIG. 4;
FIG. 6 is a block diagram of a circuit construction in a stereo
camera according to a first embodiment of the present
invention;
FIG. 7 is a flow chart of a photographing operation of a stereo
camera according to a first embodiment of the present
invention;
FIG. 8 is a perspective view of a second embodiment of a stereo
camera according to the present invention;
FIG. 9 is a schematic view of right and left photographing optical
systems having substantially parallel photographing optical axes,
in a stereo camera according to a second embodiment of the present
invention;
FIG. 10 is a schematic view of right and left photographing optical
systems whose optical axes define therebetween an angle of
convergence, in a stereo camera according to a second embodiment of
the present invention;
FIG. 11 is a block diagram of a circuitry in a stereo camera
according to a second embodiment of the present invention;
FIG. 12 is a flow chart of a photographing operation of a stereo
camera according to a second embodiment of the present
invention;
FIG. 13 is a perspective view of a third embodiment of a stereo
camera according to the present invention;
FIG. 14 is a schematic view of right and left photographing optical
systems having substantially parallel photographing optical axes,
in a stereo camera according to a third embodiment of the present
invention;
FIG. 15 is a schematic view of right and left photographing optical
systems whose optical axes define therebetween an angle of
convergence, in a stereo camera according to a third embodiment of
the present invention;
FIG. 16 is a block diagram of a circuit construction in a stereo
camera according to a third embodiment of the present invention;
and
FIG. 17 is a flow chart of a photographing operation of a stereo
camera according to a third embodiment of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the present invention will be discussed below with
reference to the drawings. FIG. 1 shows a first embodiment of a
stereo camera according to the present invention. The stereo camera
10 is an electronic still camera in which an object is photographed
using an image pickup device and is comprised of a box-shaped
housing 11 which is provided on the front portion thereof with a
pair of right and left photographing optical systems RL and LL and
on the rear portion thereof with a pair of right and left finder
eyepiece portions RF and LF.
The housing 11 is provided on its upper surface with a function
dial 12 which is adapted to turn the power source ON/OFF or select
photographing modes, and a release button 13. A pair of operation
buttons 14 and 15 are provided in the vicinity of the function dial
12 to select the frames or exposure correction value, etc. Also, an
active type infrared object distance metering device 16 is provided
on the front surface of the housing 11 and between the right and
left photographing optical systems RL and LL.
As can be seen from FIGS. 4, 5A and 5B, the right photographing
optical system RL is secured to a right photographing unit 21 in
the form of a box. Likewise, the left photographing optical system
LL is secured to a left photographing unit 22 in the form of a box.
The photographing optical systems RL and LL are each provided with
an AF lens (not shown) movable along the optical axis. The pair of
photographing units 21 and 22 in a symmetric arrangement in the
lateral direction are identical in structure.
A right CCD (first image pickup device) 23 is provided in the
photographing unit 21 behind the photographing optical system RL to
pickup an object image formed by the photographing optical system
RL. Likewise, a left CCD (second image pickup device) 24 is
provided in the photographing unit 22 behind the photographing
optical system LL to pickup an object image formed by the
photographing optical system LL. The right and left photographing
optical systems RL and LL are spaced at a distance equal to the
base length d with respect to the center point P.
A right LCD 17R in which an object image picked-up by the right CCD
23 is indicated is built in the right finder eyepiece portion RF
(see FIG. 6). Likewise, a left LCD 17L in which an object image
picked-up by the left CCD 24 is indicated is built in the left
finder eyepiece portion LF (see FIG. 6).
The right and left photographing units 21 and 22 are secured to
rotary plates 31 and 32 whose center axes of rotation C1 and C2 are
parallel. As shown in FIGS. 5A and 5B, the center axes C1 and C2 of
the rotary plates 31 and 32 pass substantially through the centers
of the corresponding photographing optical systems RL and LL and
extend in the direction perpendicular to the optical axes OR and
OL, respectively. The rotary plates 31 and 32 are provided with
sector gears 31a and 32a which are always in mesh with each other.
Consequently, the right and left rotary plates 31 and 32 are
rotatable in opposite directions in association with each other
through the sector gears 31a and 32a.
The rotary plate 32 to which the left photographing unit 22 is
secured is provided with a sector worm wheel 32b on the side
opposite to the sector gear 32a with respect to the center of
rotation C2. The worm wheel 32b is always in mesh with a worm 35a
secured to a drive shaft of a motor 35 provided in the vicinity of
the rotary plate 32. Thus, when the motor 35 is driven, the right
and left photographing units 21 and 22 are rotated about the
respective centers of rotation C1 and C2 in association with each
other. As can be seen in FIG. 5B, the diameter L1 of the gear
portion 31a is identical to the diameter L2 of the gear portion
32a, and the diameter L3 of the worm wheel 32b is larger than the
diameter L1 (L2). The rotary plates 31, 32, the gear portions 31a,
32a, the worm wheel 32b, the worm 35a, and the motor 35, etc., form
a drive mechanism which constitutes a convergence angle adjustment
mechanism 45 (FIG. 6).
In FIG. 2, the optical axes OR and OL of the right and left
photographing units 21 and 22 are substantially parallel, i.e., the
right and left photographing optical systems RL and LL have no
angle of convergence. In FIG. 3, the optical axes OR and OL of the
right and left photographing units 21 and 22 intersect at a point
in front of the stereo camera 10, i.e., the right and left
photographing optical systems RL and LL define an angle of
convergence therebetween. In FIGS. 2 and 3, "d" designates the base
length, "S" the main object, "f.sub.o" the object distance,
".theta." a half angle of convergence (i.e., 2.theta. represents
the angle of convergence), and "P" the origin located at the median
point of the right and left photographing optical systems RL and
LL, respectively.
FIG. 6 shows a block diagram of a circuit of the stereo camera 10
according to the first embodiment. The stereo camera 10 has a
system controller (control circuit) 40 in the form of a
microcomputer, etc., for generally controlling the camera 10.
Connected to the controller 40 are a release switch 13a which is
turned ON/OFF in accordance with the operation of the release
button 13, operation switches 14a and 15a which are respectively
turned ON/OFF by the operation of the operation switches 14 and 15,
and a function dial switch 12a whose state is varied in accordance
with the operation of the function dial 12. The release switch 13a
is a two-step switch which detects half depression and full
depression of the release button 13.
An object distance measuring device 16, a first lens drive circuit
41 which drives the AF lens of the right photographing optical
system RL, a second lens drive circuit 42 which drives the AF lens
of the left photographing optical system LL, a first CCD drive
circuit 43 which drives the right CCD 23, a second CCD drive
circuit 44 which drives the left CCD 24, and a convergence angle
adjustment mechanism 45 are connected to the system controller 40.
In addition to the foregoing, a first LCD drive circuit 46 which
drives the right LCD 17R and a second LCD drive circuit 47 which
drives the left LCD 17L are connected to the system controller
40.
Also connected to the system controller 40 are a first CDS/AGC
circuit 48 connected to the right CCD 23, a second CDS/AGC circuit
49 connected to the left CCD 24, a first A/D converter 50, a second
A/D converter 51, a memory 52, a signal processor 53, and a memory
controller 54. An image recording device 55 which records image
data in a recording medium (not shown) such as a floppy disc or a
flash memory, etc., is connected to the memory controller 54.
The image signal obtained through the right CCD 23 is subject to an
A/D conversion by the first A/D converter 50 through the first
CDS/AGC circuit 48 and is stored in the memory 52. Likewise, the
image signal obtained through the left CCD 24 is subject to an A/D
conversion by the second A/D converter 51 through the second
CDS/AGC circuit 49 and is stored in the memory 52. The image
signals stored in the memory 52 are processed by the signal
processor 53 and are fed to the right LCD 17R and the left LCD 17L.
Also, the signal processor 53 sends the same image signal as those
fed to the right and left LCDs 17R and 17L to the memory controller
54. The image signal fed to the memory controller 54 is recorded on
a recording medium such as a floppy disc or a flash memory, etc.,
by the image memory device 55 as image data when the release button
13 is depressed to turn the release switch 13a ON.
FIG. 7 shows a flow chart of the photographing operation in the
stereo camera 10 according to the first embodiment. When the power
source of the stereo camera 10 is turned ON, the right and left
CCDs 23 and 24 are driven, and the right and left LCDs 17R and 17L
are driven (S101, S103). Thereafter, a passive object distance
measurement is carried out in each of the right and left CCD 23 and
24 (S105). In this operation, the measurement point for the right
CCD 23 is located in the left side area of the field angle (e.g.,
substantially at the center of the left half of the field angle)
with respect to the median line thereof. Likewise, the measurement
point for the left CCD 24 is located in the right side area of the
field angle (e.g., substantially at the center of the right half of
the field angle) with respect to the median line thereof.
The photometering operation (brightness measurement) is carried out
in each of the right and left CCDs 23 and 24 (S107). Thereafter, a
mean value of the first measurement (first object distance)
obtained by the right CCD 23 and the second measurement (second
object distance) obtained by the left CCD 24 is calculated ([1st
object distance+2nd object distance]/2). Subsequently, a mean value
of the first photometering measurement (first brightness) obtained
by the right CCD 23 and the second photometering measurement
(second brightness) obtained by the left CCD 24 is calculated ([1st
brightness+2nd brightness]/2) (S109, S111). Consequently, the AE/AF
control operations are carried out in accordance with the mean
object distance obtained at step S109 and the mean brightness
obtained at step S111 (S113).
If it is detected that the release button 13 is depressed by half a
step (S115), the control proceeds to step S117. If it is not
detected that the release button 13 is depressed by half a step,
the control is returned to step S105. Namely, the operations from
step S105 to step S115 are repeated so long as the release button
13 is not depressed by half a step after the power source is turned
ON.
If it is detected that the release button 13 is depressed by half a
step at step S115, the active measurement of the object distance is
carried out by the object distance measuring device 16 to obtain
the object distance f.sub.o. Consequently, the convergence angle
adjustment mechanism 45 (i.e., the motor 35) is driven in
accordance with the object distance to provide an angle of
convergence between the right and left optical axes OR and OL
(S117, S119).
Thereafter, the measurements of the brightness (photometering) are
carried out again in the right and left CCDs 23 and 24, similar to
those at step S107. Thereafter, similar to the operation at step
S111, a mean value of the first measurement (first brightness)
obtained by the right CCD 23 and the second measurement (second
brightness) obtained by the left CCD 24 is calculated in accordance
with ([1st brightness+2nd brightness]/2) (S121, S123).
Consequently, the AE control is carried out in accordance with the
mean brightness thus obtained (S125).
If it is detected that the release button 13 is depressed by a full
step, the control proceeds to step S129. If it is not detected that
the release button 13 is depressed by a full step, the control
proceeds to step S131 (S127). If the release button 13 is depressed
by a full step, the memory controller 54 and the image recorder 55
are driven to record the image data in the recording medium (not
shown), such as a floppy disc or a flash memory (S129). After the
recording operation is completed, the angle of convergence is
returned to a predetermined initial value and the control is
returned (S133).
If it is detected at step S127 that the release button 13 is not
depressed by a full step, it is checked whether the release button
13 has been released from a half step depression (S131). If it is
detected that the half depression of the release button 13 is not
released, (i.e., the half depression of the release button 13 is
maintained), the control is returned to step S127 to repeat steps
127 and S131. If it is detected that the half depression of the
release button 13 is released, the control proceeds to step S133
(S131: Y; S133).
In the operation at step S119, the angle of convergence is
determined in accordance with the following equation (1):
.theta.=tan.sup.-1(d/2f.sub.o) (1)
wherein ".theta." represents the half angle of convergence
(degrees), "f.sub.o" represents the object distance (m), and "d"
represents the base length (mm) between the right and left
photographing optical systems RL and LL. The object distance
f.sub.o is determined at step S117 in FIG. 7.
Table 1 below shows the relationship between the object distance
f.sub.o and the angle .theta. when the base length is 65 mm (d=65
mm).
TABLE-US-00001 TABLE 1 f.sub.o (m) .theta. (.degree.) 1 1.861 2
0.931 5 0.372 10 0.186
FIG. 8 shows a second embodiment of a stereo camera according to
the present invention. The stereo camera 100 is an electronic still
camera similar to the stereo camera 10 in the first embodiment. The
camera 100 includes a box-like housing 101 which is provided on the
front surface thereof with right and left photographing optical
systems RL and LL, and on the rear surface thereof with right and
left finder eyepiece portions RF and LF, respectively. In the
stereo camera 100 according to the second embodiment, elements
corresponding to those in the first embodiment are designated with
like numerals.
Unlike the first embodiment in which the right and left
photographing units 21 and 22 are rotated to vary the angle of
convergence, variable angle prisms (prisms whose apex angle is
variable) RV and LV (see FIG. 9) are provided in each light path of
the right and left photographing optical systems RL and LL, so that
the variable angle prisms are driven to vary the angle of
convergence, in the second embodiment. The right and left
photographing units 21 and 22 are secured to the box-like housing
101 in the second embodiment.
The stereo camera 100 is provided with variable angle prisms RV and
LV on the object sides of the right and left photographing optical
systems RL and LL (see FIGS. 9 and 10). In FIG. 9, no angle of
convergence is provided by the variable angle prisms Rv and LV,
i.e., the optical axes OR and OL of the right and left
photographing units 21 and 22 are parallel. In FIG. 10, an angle of
convergence is provided by the variable angle prisms RV and LV. In
FIGS. 9 and 10, ".PHI." represents the variable apex angle
(.degree.) of the variable angle prisms RV and LV.
FIG. 11 shows a block diagram of a circuit in a stereo camera 100
according to the second embodiment. In the second embodiment, the
convergence angle adjustment mechanism 45 provided in the circuit
of the stereo camera 10 in the first embodiment is replaced with a
variable angle prism (VAP) control apparatus 60 connected between
the variable angle prisms RV, LV and the system controller (control
circuit) 40. The VAP control apparatus 60 is controlled by the
system controller 40 and drives the variable angle prisms RV and LV
in accordance with the object distance f.sub.o obtained to vary the
apex angle .PHI. of the variable angle prisms RV and LV. Other
circuit elements in the second embodiment are the same as those of
the circuit in the first embodiment shown in FIG. 6. In the stereo
camera 100 according to the second embodiment, the variable angle
prisms RV, LV and the VAP control apparatus 60, etc., constitute
the convergence angle adjustment mechanism.
FIG. 12 shows a flow chart of the photographing operation of the
stereo camera 100 according to the second embodiment. In the flow
chart, the operation at step S119 in the flow chart of the
photographing operation of the stereo camera 10 according to the
first embodiment shown in FIG. 7 is replaced with the variable
angle prism (VAP) control operation (S118). Other operations in
FIG. 12 are identical to those in FIG. 7.
Namely, after the active measurement of the object distance at step
S117 is completed, the variable angle prisms RV and LV are driven
to vary the apex angles .PHI. of the variable angle prisms RV and
LV, so that a desired angle of convergence can be provided between
the right and left optical axes OR and OL (S118). Thereafter, the
control proceeds to step S121.
At step S118 in the second embodiment, the variable apex angle
.PHI. is determined in accordance with the following expression
(2): .PHI.=(n-1).theta. (2)
wherein ".PHI." represents the variable apex angle (.degree.) "n"
represents the refractive index of the variable angle prisms RV and
LV, and ".theta." represents half of the convergence angle
(deflection angle) (.degree.), respectively.
Table 2 below shows a relationship between the object distance
f.sub.o and the variable apex angle .PHI. when the base length d is
65 mm and the refractive index n is 1.5, respectively, in the
stereo camera 100 according to the second embodiment.
TABLE-US-00002 TABLE 2 f.sub.o (m) .PHI. (.degree.) 1 0.931 2 0.466
5 0.186 10 0.093
FIG. 13 shows a third embodiment of a stereo camera according to
the present invention. The stereo camera 200 is an electronic still
camera similar to the stereo camera 10 in the first embodiment. The
camera 200 includes a box-like housing 101 which is provided on the
front surface thereof with a pair of right and left photographing
optical systems RL and LL, and on the rear surface thereof with a
pair of right and left finder eyepiece portions RF and LF,
respectively. In the stereo camera 200 according to the third
embodiment, elements corresponding to those in the first embodiment
are designated with the same reference designators.
Unlike the first embodiment in which right and left photographing
units 21 and 22 are rotated to vary the angle of convergence, or
the second embodiment in which right and left variable angle prisms
RV and LV are driven to vary the angle of convergence, in the third
embodiment, the right and left photographing optical systems RL and
LL are shifted (decentered) in a direction of the base length
thereof to vary the angle of convergence. The right and left
photographing optical systems RL and LL are movable in the lateral
direction (right and left direction in FIGS. 14 and 15) to move
away from or close to each other within the corresponding
photographing units 21 and 22, in the stereo camera 200. Moreover,
in the stereo camera 200, first and second lens shift actuators
(lens drive mechanisms) 61 and 62 (FIG. 16) are provided to move
the right and left photographing optical systems RL and LL in the
directions away from or close to each other. The drive mechanism
can be achieved by any known drive mechanism, for example, a
combination of a motor and a cam mechanism or an electromagnetic
drive mechanism having a coil combined with a magnet.
In FIG. 14, the shift (off-axis amount) of the photographing
optical systems RL and LL from the CCDs 23 and 24 in the
photographing units 21 and 22 is zero, and hence no angle of
convergence is provided (i.e., the optical axes OR and OL of the
right and left photographing units 21 and 22 are parallel). In FIG.
15, the photographing optical systems RL and LL are shifted by y
(mm) from the CCDs 23 and 24 in the photographing units 21 and 22,
so that a predetermined angle of convergence is provided. In FIG.
15, ".omega." represents half of the angle of convergence
(.degree.), "f" represents the focal length of the lens (mm), and
"y" represents the shift amount (mm) of the photographing optical
systems RL and LL, respectively.
FIG. 16 shows a block diagram of a circuit in a stereo camera 200
according to the third embodiment. In the third embodiment, the
convergence angle adjustment mechanism 45 provided in the circuit
of the stereo camera 10 in the first embodiment is replaced with a
first lens shift actuator 61 which is connected between the right
photographing optical system RL and the system controller 40, and a
second lens shift actuator 62 which is connected between the left
photographing optical system LL and the system controller 40. The
first lens shift actuator 61 is controlled by the system controller
40 to move the right photographing optical system RL by the amount
of shift (displacement) "y" in accordance with the object distance
"f.sub.o" obtained. Likewise, the second lens shift actuator 62 is
controlled by the system controller 40 to move the left
photographing optical system LL by the amount of shift
(displacement) "y" in accordance with the object distance "f.sub.o"
obtained. Other circuit elements in the third embodiment are the
same as those of the circuit in the first embodiment shown in FIG.
6. In the stereo camera 200 according to the third embodiment, the
first lens shift actuator 61 and the second lens shift actuator 62,
etc., constitute a convergence angle adjustment mechanism.
FIG. 17 shows a flow chart of the photographing operation of the
stereo camera 200 according to the third embodiment. In the flow
chart, the operations at steps S119 and S133 in the flow chart of
the photographing operation of the stereo camera 10 according to
the first embodiment shown in FIG. 7 are replaced with lens shift
actuator control operation (S120) and the return operation of the
lenses (photographing optical systems RL and LL) to the initial
positions (S134), respectively. Other operations in FIG. 17 are the
same as those in FIG. 7.
Namely, after the active measurement of the object distance at step
S117 is completed, the lens shift actuators 61 and 62 are driven in
accordance with the object distance thus obtained to move or shift
the photographing optical systems RL and LL (S120). Thereafter, the
control proceeds to step S121. At step S134, the photographing
optical systems RL and LL are returned to the preset initial
positions and thereafter, the control is returned to step S105.
At step S120 in the third embodiment, the amount of shift
(displacement) is determined in accordance with the following
expression (3); y=ftan .omega. (3) tan .omega.=0.5d/(f.sub.o+f)
wherein "y" represents the amount of shift (displacement) (mm), "f"
represents the focal length of the lens (mm), ".omega." represents
half of the convergence angle (.degree.), and "d" represents the
base length between the right and left photographing optical
systems RL and LL, respectively.
Although the variable angle prisms RV and LV are provided on the
object sides of the right and left photographing optical systems RL
and LL in the second embodiment, the arrangement of the variable
angle prisms is not limited thereto. Namely, the variable angle
prisms can be located at any positions within the light paths of
the right and left photographing optical systems RL and LL. For
instance, the same technical effect can be expected from an
alternative arrangement in which the variable angle prisms RV and
LV are provided within the corresponding photographing optical
systems RL and LL.
Although, in the third embodiment, the right and left photographing
optical systems RL and LL are moved with respect to the optical
axes OR and OL thereof in the directions perpendicular to the
optical axes to vary the angle of convergence, the invention is not
limited thereto. For instance, in an alternative, it is possible to
move at least part of the photographing optical systems RL and LL
in directions normal to the optical axes OR and OL, respectively.
In this alternative, the same effect as the previous embodiments
can be obtained.
Although the above-mentioned embodiments are applied to an
electronic still camera, the present invention can be equally
applied to a stereo camera using silver halide films which replace
the CCDs 23 and 24, respectively.
As may be understood from the foregoing, in a stereo camera
according to the present invention, since the convergence angle
adjustment mechanism is automatically controlled to vary the angle
of convergence defined between the optical axes of a pair of
photographing optical systems to adjust the photographic coverage
of the pair of photographic optical systems so as to coincide with
each other, in accordance with the object distance data, it is
possible to easily set an appropriate angle of convergence between
the right and left optical axes without need of a complex operation
to thereby obtain a high-quality three-dimensional picture, even if
the object distance is relatively small or the telephotographic
photographing systems are used.
Obvious changes may be made in the specific embodiments of the
present invention described herein, such modifications being within
the spirit and scope of the invention claimed. It is indicated that
all matter contained herein is illustrative and does not limit the
scope of the present invention.
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